Ion channels are critical mediators of numerous physiological processes. They are not only important therapeutic targets themselves, but their unintended modulation can also cause unwanted drug side effects. This presentation will focus on strategies to identify new ion channel targets and on high throughput methodologies to dial out undesired ion channel interactions.

Cystic Fibrosis is a genetic, lethal, and multi-organ disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a cyclic-AMP-regulated chloride ion channel that also modulates epithelial sodium channels. Mutations in CFTR lead to decreased chloride secretion and increased sodium absorption across airway epithelia, resulting in reduced hydration of the airway surface, decreased mucociliary clearance, and chronic mucus plugging/airway obstruction. Most CF patients die from progressive loss of lung function associated with chronic lung inflammation and opportunistic bacterial infection. Denufosol is an inhaled ion channel regulator that stimulates an alternative calcium-activated chloride channel in airway epithelial cells via agonism of the P2Y2 nucleotide receptor. Denufosol also inhibits sodium absorption and increases ciliary beat frequency and these integrated pharmacological actions of denufosol are expected to correct the ion transport defect in CF via a mechanism of action that is independent of CFTR function. This presentation will present the denufosol program as a case study focusing on the value of leveraging scientific data and insights gained throughout R&D to better understand and optimize the therapeutic potential of an investigational drug with a novel MOA in a rapidly changing and highly competitive treatment landscape.

Sponsored by11:10 The IonWorks Barracuda System, a 384-Well Automated Electrophysiology Platform for Ligand- or Voltage-Gated Ion ChannelsKaren Cook, M.S., Application Scientist, Automated Electrophysiology, Molecular Devices, Inc.An introduction to the IonWorks Barracuda system will be presented including validation data collected from Ligand- (LGIC) and Voltage-Gated (VGIC) channels. The system allows simultaneous and continuous measurement of ionic currents at 384 separate recording sites. Currents are measured using a single hole (SH) or an array of 64 holes in each well (PPC). We will present data collected on the IonWorks Barracuda system in both SH and PPC modes. Pharmacological blockade of ion channel activity is also presented to validate the use of the IonWorks Barracuda system for screening ion channel targets in a drug discovery setting.

11:40 Discovery and Development of CFTR Modulators for the Treatment of Cystic FibrosisFredrick VanGoor, Ph.D., Scientist II, Vertex Pharmaceuticals
Cystic Fibrosis (CF) is caused by genetic mutations that result in a malfunctioning or missing CF Transmembrane Conductance Regulator (CFTR) chloride channel at the cell surface of epithelial cells. Pharmacological agents that repair the underlying molecular defects in CFTR due to gene mutations offer hope for the treatment of CF. Vertex is pursuing two complementary approaches to repair mutant CFTR function. The first approach is to identify small molecules that increase the cellular processing and delivery of mutant CFTR proteins, such as F508del-CFTR, to the cell surface. These agents are called CFTR correctors and are exemplified by VX-809. The second approach is to identify small molecules that increase the channel gating activity of mutant CFTR located at the cell surface. These agents are called CFTR potentiators and are exemplified by VX-770.

Acute modulation of thyroid hormones on ion channels through non-genomic pathways has attracted increasing research attention. Using a whole-cell patch clamp recording method to study sodium channel currents (INa) of human skeletal muscle type (hNav1.4) that are stably expressed in HEK 293 cells, we show that physiological concentrations of L-thyroxine (T4, 10-6 M) rapidly enhanced INa by 40.9% (activated at -30 mV, n=10). The enhanced INa was associated with a 10 mV negative shift in INa activation threshold (-50 mV vs. -60 mV) 20 mV negative shift in maximal INa activation (-20 mV vs. -40 mV), implying a T4 mediated rapid modulation of open state of sodium channels. In contrast, the potentiation of INa could not be reproduced by 3, 5, 3’-triiodo-L-thyronine (T3), a genomically active form of thyroid hormone. Selective and rapid modulation of sodium channels by T4, but not T3, suggests a unique role of T4 in the nongenomic regulation of the physiological activity of sodium channels. We will establish that this effect of T4 is indeed non-genomic and mediated by the plasma membrane hormone receptor, integrin avb3.

Insulin-independent glucose turnover is becoming a focus of attention in drug discovery for Type 2 Diabetes. In this presentation two lines of evidence will be presented to support that Kv1.3 fits this category and should be considered as a unique target for treating the disease: insulin-independent glucose clearance in human cells through selective blocking of Kv1.3 channels, and differential effects of Kv1.3-selective compound in wild-type and Kv1.3-deficient mice.

A variety of ion channels have been detected in cancer cells and tissues. This is an epigenetic phenomenon and not a passive byproduct of the cancer process. In particular, metastatic breast and prostate cancer (and several other carcinomas) express functional voltage-gated sodium channels, activity of which enhance the cells’ invasiveness. Importantly, these sodium channels are neonatal splice variants not seen in normal adult tissue. This enabled generation of a cancer-specific blocking antibody.

The “CLC” family of chloride channels and transporters are fundamental to all of physiology, with functions ranging from the regulation of bone mineralization, muscle excitability, neuronal activity, fluid/electrolyte balance and blood pressure, to the facilitation of extreme-acid tolerance in pathogenic bacteria. A major roadblock in studying the CLC proteins has been the dearth of specific small-molecule inhibitors, which could be used to probe protein function on the molecular and cellular level, and to treat CLC-mediated disorders. Our research is aimed at overcoming this roadblock by developing novel chloride-channel inhibitors with improved affinities and specificities.

4:35 Identification and Optimization of Novel Thienopyrimidines as Inhibitors of the Kv1.5 Voltage-Gated Potassium Channel

Atrial fibrillation is one of the more common cardiac arrhythmias, with estimates of around 11M people affected in the seven major economies. Current therapies are considered to be poor, with many patients suffering adverse side-effects, including pro-arrhythmic events. One of the approaches considered to be viable for reducing the incidence of AF is to extend the atrial repolarisation period, thereby reducing the inherent electrical excitability of cardiac myocytes. Recent studies have demonstrated that the ultra-rapid delayed rectifier current, IKur (carried by the Kv1.5 channel) is predominantly found in human atrial cells and therefore offers the potential for selective intervention in the repolarising phase of atrial currents. The discovery and optimization of a novel series of heterocyclic Kv1.5 channel blockers will be is reported.